There is a consistent requirement in the commercial marketplace for the packaging of a specific number of elements in a container, and a wide variety of systems are available for this purpose. One of the known techniques involves weighing of an accumulated batch of workpieces and comparing the weight against a calculated total weight of the desired number of elements. This technique frequently has accuracy limitations, necessitating the practice of overfilling or overcounting to avoid the possibility of a short count. This technique also tends to have limitations on speed at which operations take place.
Other known techniques involve passing the workpieces or elements, one at a time, past a counter device, usually a photosensor or other optical device requiring no contact with the part being counted. A particularly advantageous form of such a system involves the use of precision centrifugal feeders, such as those marketed by the Hoppmann Corporation, of Chantilly, Va. The Hoppmann centrifugal feeder utilizes a rotating bowl having a confined ledge or flange arranged to receive the parts in a single-file order, that is, the flange is too narrow to support two elements in side-by-side relation, and means are provided for preventing workpieces from stacking vertically, one above the other. As individual workpieces are carried by the flange-of the rotating bowl, means are provided for inducing linear separation between successive elements, after which they are optically counted by momentary interruption of a light beam as individual workpieces pass by. As soon as the workpieces pass the counter, they are caused to exit the system through a sidewall opening, allowing momentum and centrifugal force to discharge the workpiece. When a desired number of workpieces has been counted, the continued flow of workpieces toward the exit opening is interrupted, typically by the action of an air jet which blows workpieces off the flange of the rotating bowl before they can reach the exit opening. As soon as the counted batch of workpieces has been collected and removed, counting of the second batch can be initiated.
While the above described system is satisfactory in many respects, certain significant speed limitations are imposed by the need for separating and individually counting the workpieces.
In accordance with one feature of the present invention, the speed at which the counting of workpieces takes place may be greatly increased without sacrifice of accuracy. In the system of the invention, provision is made for electronically counting minute increments of advancing movement of the workpiece conveyor, preferably the bowl flange of a Hoppmann-type centrifugal feeder device. For any particular workpiece to be processed, the length of that workpiece can be accurately ascertained, and the total length of a given number of such workpiece can also be accurately ascertained. In the system of the invention, once the total length of a workpiece, and the desired number of workpieces, are known, that information is converted to an appropriate number of electronically countable motion increments of the conveying device. The movement of workpieces past a counting point is detected by a sensor, preferably an optical switch arranged to respond to a light beam. At any time that the light beam is interrupted, increments of movement of the conveyor means are electronically counted, and a total of increments is accumulated.
In the system of the invention, it is immaterial whether the workpieces are separated individually or pass by the sensor in tightly contacting groups. For example, if a group of three workpieces pass by the sensing point in end-to-end contact, the light beam is caused to be continuously interrupted throughout the passage of all three workpieces. However, motion increments of the conveying flange, corresponding to the combined length of all three workpieces, are detected and counted during the light beam interruption. Once the total increment count equals the precalculated count for the desired total number of workpieces, the continued passage of workpieces to the exit point is interrupted while the just-counted batch is removed, after which counting of a new batch is initiated.
By eliminating the need for effecting linear separation of successive workpieces during their passage past the sensing means, it becomes possible to operate the workpiece conveyor at much higher speeds. This is particularly true in the case of the preferred conveyor, namely a rotating bowl, because manipulation of the workpieces becomes increasingly difficult with higher rotating speeds, partly because of the greater centrifugal forces involved, and partly because of the increased momentum of the workpieces.
In known systems for counting workpieces using, for example, Hoppmann-type centrifugal feeders, it is typical to employ air jet diverter means to displace workpieces from the flange of the rotating bowl during the interim period between the counting of successive batches. In the system of the present invention, because of the significantly higher rotating speeds made possible, and the higher centrifugal forces engendered thereby, air jet deflector means is somewhat less reliable than is desired, resulting in the potential for the passing of occasional uncounted workpieces. In the system of the present invention, positive mechanical deflector means are deployed in the short interval between the counting of successive batches, reliably preventing the passage of uncounted workpieces to the exit opening. In addition, associated air jet deflector means is positioned somewhat upstream of the mechanical diverter. The air jet diverter removes the majority of workpieces from the flange of the rotating bowl, and any workpieces which the air jet fails to divert are shortly thereafter positively deflected off of the flange by the deployed mechanical diverter. The mechanical diverter, in combination with an upstream air jet diverter assures positive control of the parts while minimizing any damage to workpieces from impacting the mechanical diverter while travelling at high speed.
Another feature incorporated in a preferred embodiment of the invention is a high speed collection-discharge system for accumulating a counted batch of workpieces in a high speed manner and, when predetermined batch count has been realized, discharging the accumulated batch of workpieces in the shortest practical time, to enable counting of a new batch to commence with a minimum of delay. To advantage, this can be realized by providing a confined conduit for guiding workpieces from the exit opening of the centrifugal feeder to a batch collector, with controlled air flow to accelerate the travel of workpieces through the conduit. The batch collector device advantageously is a gravity fed collecting box, with hinged bottom panels for releasing and discharging a batch of counted workpieces into a suitable container. Advantageously, the collecting box has a perforate bottom structure, such that augmented air flow used in conveying workpieces toward the collecting box exits through the bottom of the box and thus serves to assist gravity in transporting workpieces quickly to the bottom of the collection box.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment of the invention and to the accompanying drawings.